You don't need to re-encrypt the drive every time the key changes, you simply re-encrypt the file containing the randomly generated key for the drive.

This is a much better use for tilting trains. Camber the track such that the trains don't need to tilt at their design speed but if the train has to run much slower on that track then they can tilt the opposite direction and make things more comfortable for the passengers.

My grandfather did this for several years back in the 1970s, except it was two second hand non-deep-cycle car batteries. Enough for lighting but not a great deal else.

Nuclear reactors have been used in space before, the soviets used them in some radar satellites. The shielding isn't really a problem once it's in space so a reactor could be designed with just enough shielding to contain the initial radioactivity of the fuel without worrying about shielding the much higher radiation levels once the reactor is operating. The shielding that it does have could also be jettisoned fairly early on in the mission.

I will agree however that RTGs are much more reliable and as such are desirable for deep space missions where the power requirements are not too high.

I remember reading in some sci fi book about a vault that was sealed by attaching a chunk of a long-lived radioisotope to the back of a tight fitting steel door such that the heat released caused the door to expand and jam tightly into the frame. The idea was that it could only be opened by a fairly advanced civilisation that was capable of artificial refrigeration, plus of course able to recognise what was needed. I always found that an intriguing idea although anyone sufficiently determined could probably get in anyway

Don't suppose anyone knows what book that was? I've been trying to find it for years now.

Me too, I also search my pockets for my phone whilst talking to someone on it.

BTU as in British Thermal Unit? It's a unit of energy so you can measure your electricity consumption in it if you want. It'd be a bit inconvenient to calculate expected use unless all your appliances state consumption in BTU per fortnight or something.

If you don't have a problem with computer monitors at over 75 Hz then I'm surprised you do with any fluorescents. The old ones with magnetic ballasts flicker at double the mains frequency (so 100 or 120 Hz), the newer electronic ones drive the tubes at about 40 kHz and the persistence of the phosphor will even out any variations in light at those frequencies. Some tubes that are very nearly dead (burnt out cathode) might conduct in only one direction and give a mains frequency flicker that most people would notice but these should only be exceptional cases.

I'll agree with you on the spectrum though, although halogen is very similar to other incandescent lights. Given that humans can't perceive absolute colour I seriously doubt a slightly shifted black body spectrum would be noticeable apart from that when side-by-side with a conventional incandescent the halogen is slightly less yellow.

That is a good point however the problem with Apollo 1 was not just the pure oxygen atmosphere but the fact that it was at atmospheric pressure. Pure oxygen at 3 psi (the apollo capsules were at this pressure whilst in space) has the same partial pressure as air at atmospheric pressure and chemically behaves the same (including both fire and biological uses).

Either an adiabatic or an isothermal process will allow high efficiency. In the adiabatic process the heat from compression is stored in the air and in principle no energy is lost through the compression and decompression. In an isothermal process all of the extra heat from the compression is transferred to some external reservoir (ocean, atmosphere, etc). If this heat is transferred back to the air when decompression occurs the air leaves the system at its original temperature (as for an adiabatic process) and no energy is lost. An isothermal system can actually store more energy since the stored air is at low temperature and hence a greater quantity may be stored within a given volume and pressure limit.

In real systems what happens is heat is lost during compression and in storage and that heat is not fully returned to the system during decompression. The air leaves at a lower temperature and energy is lost. Some compressed air energy storage schemes have resorted to using natural gas to reheat the air since heat exchangers for a true isothermal process are impractically large.

Now that is a good idea. Since such a tank would be large we could store it external to the train and have valves along the length of the tunnel which can be remotely operated from on board the train. Perhaps we could confine this external source of air gravitationally rather than in a tank and call it the atmosphere?

Seriously though, that's all that would be needed. You could include one oxygen mask for someone to go out and open the next valve down if it gets stuck or something like that. Bear in mind that 3 psi isn't that low - humans are quite happy at that pressure if they're breathing pure oxygen - that's what was used on the apollo moon missions.

I haven't studied or spoken German in a long time but that's how I would have translated his example based on what I was taught at school. I would think that when spoken by someone who clearly isn't a native speaker any excessive formality would be ignored.

Anyone know why I get a blank white page with the words “None shall pass.” when I visit that link?

Effectively zero electrons make it through, it's probably a less significant effect than the tritium diffusing through the glass (which is also insignificant). What does escape through the glass is bremstrahlung, X-ray radiation produced when the electrons strike the glass wall of the container. It's still too weak to be a health risk and the plastic outer can will absorb quite a bit since they're very low energy but it is detectable. If you took the inner glass capsule out and placed it on a sheet of photographic film wrapped in foil to block the light and came back in a few months to develop it you'd see a dark line where it was sitting.

I have a couple of these, one on my keyring and one on my penknife - they're very useful to tag things so you can find them if you drop them and the keyring one also helps me find the right key in the dark.

I was about to do that conversion, I'm not sure if the silly “parts per litre” units are something used in the industry to avoid exponential notation or something made up by the greenpeace press office to make the concentration sound a lot bigger than it is. I'm guessing to actually measure this they'd measure the activity of the water per unit mass (Bq kg^-1) and convert but I suppose they could also do it with a mass spectrometer which would also show up any other contamination.